Transfer Substrate with Differential CTE for Micro LED Alignment
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Solution Overview
Problem
The expansion of transfer substrates during heating processes in micro LED component transferring leads to reduced alignment accuracy and lower yields due to differences in thermal expansion coefficients between the substrate materials, causing structural misalignment and damage.
Innovation Solution
A transfer substrate design with a base and transfer heads having different thermal expansion coefficients (CTEs) than the micro components, where the CTE difference between the base and transfer heads is controlled to minimize misalignment, and an adhesion layer on the transfer heads enhances component fixation and alignment precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transfer substrate is heated to fix or release micro light emitting components, then the transferring process can be completed, but the structure of the transfer substrate expands, lowering the alignment accuracy
Solution Approach 1:
The patent applies thermal expansion principle by designing the transfer substrate with a base and transfer heads made of different materials having different coefficients of thermal expansion (CTE). The base has a higher CTE than the transfer heads, causing the base to expand more during heating, which maintains the relative position of transfer heads and improves alignment accuracy despite thermal heating
Solution Approach 2:
The transfer substrate uses composite material structure with a base and transfer heads made of different materials. The base may be made of materials like silicon or glass with higher CTE, while transfer heads are made of materials with lower CTE. This composite structure allows differential thermal expansion to compensate for alignment errors during heating processes
2Temperature
If the transfer substrate structure expands during heating, then thermal processes can be completed, but the alignment accuracy of structures to micro light emitting components is reduced
Solution Approach 1:
The patent utilizes thermal expansion by designing the base with higher CTE than transfer heads. During heating, the base expands more than the transfer heads, creating a compensatory effect that maintains the relative positioning accuracy of transfer heads with respect to micro components on the source substrate
Solution Approach 2:
The differential CTE design预先 (in advance) compensates for the expected thermal expansion misalignment. By having the base expand more than the transfer heads during heating, the system pre-counters and offsets the potential alignment errors before they affect the transferring process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures precise alignment and transfer of micro components, reducing process defects and increasing overall yields by managing thermal expansion and maintaining structural integrity during heating processes.
Implementation Method 1
a coefficient of thermal expansion (CTE) of the base is different from CTEs of the transfer heads, with a difference between the CTE of any one of the transfer heads and a CTE of any one of the micro components is less than another difference between the CTE of the base and the CTE of any one of the transfer heads
Data Source
AI summary
A transfer substrate is configured to transfer a plurality of micro components from a first substrate to a second substrate. The transfer substrate comprises a base and a plurality of transfer heads. The base includes an upper surface. The plurality of transfer heads is disposed on the upper surface of the base, wherein each transfer head includes a first surface and a second surface opposite to each other and the transfer heads contact the base with the first surfaces thereof. A plurality of adhesion lumps is separated from each other, wherein each adhesion lump is disposed on the second surface of one of the transfer heads. A CTE of the base is different from CTEs of the transfer heads.